Automatic operations on materials

Abstract

Method and Apparatus for guiding an operation effector such as a laser cutter to effect an operation along a path on a patterned material using machine vision. The machine vision is used to make a map of a repeat of the pattern, a path is defined on the map by drawing a line on an area image map of the repeat of the pattern, the material and operation effector are moved relatively along the direction of pattern repeat, a line scan camera scans the material during a relative movement between the camera and the patterned material and a scanning image is compared with the map to determine the relative positions of the material and the operation effector, and the operation effector is guided to effect the operation at a position on the material corresponding to the path defined on the map.

We claim: 
     
       1. A method of guiding an operation effector to effect an operation along a path on a repeatedly longitudinal patterned material using machine vision, in which method: (a) machine vision is used to make a map of a repeat of the pattern across the width of the material;   (b) a path is defined on the map by drawing a line on an area image map of the complete repeat of the pattern, said line extending the length of the repeat of the pattern;   (c) the material and operation effector are moved relatively along the lengthwise direction of the repeat of the pattern;   (d) the machine vision scans the pattern of the material during the relative movement of the material and operation effector, and forms a scanning image;   (e) the scanning image is compared with the map to determine the relative positions of the material and the operation effector; and   (f) the operation effector is guided to effect the operation at a position on the material corresponding to the path defined on the map.   
     
     
       2. A method according to claim 1, characterised in that the map is displayed as an image on a screen and a pointing device is used to define the path on the screen image. 
     
     
       3. A method according to claim 1, in which the machine vision comprises a line scan camera used to build up the map and also used to produce the scanning image. 
     
     
       4. A method according to claim 1, in which the map and the scanning image are pixel images and a cross-correlation algorithm is used to establish correlation between a line of pixels on the map and a line of pixels on the image. 
     
     
       5. A method according to claim 4, in which the cross-correlation algorithm is weighted towards the centre of the map. 
     
     
       6. A method according to claim 4, in which the cross-correlation algorithm compensates for lateral displacement or distortion of the material with respect to its mapping position. 
     
     
       7. A method according to claim 4, in which the cross-correlation algorithm compensates for lateral displacement or distortion of the material with respect to its mapping configuration. 
     
     
       8. A method according to claim 1, in which the material is lace and the operation is a cutting operation. 
     
     
       9. A method according to claim 8, in which the cutting operation involves cutting along a scalloped edge. 
     
     
       10. A method according to claim 8, in which the cutting operation involves cuts along a line that crosses a line transverse to the direction of relative movement of material and operation effector more than once. 
     
     
       11. A method according to claim 10, in which said line comprises a closed curve. 
     
     
       12. A method according to claim 1, in which the operation effector comprises a laser. 
     
     
       13. A method according to claim 1, in which map and scanning image are compared automatically at the beginning of an operation to define a start point. 
     
     
       14. Apparatus for guiding an operation effector to effect an operation along a path on a patterned material using machine vision, characterized by a machine vision system adapted to make and display a map of a repeat of the pattern, means to define a path on the map by drawing a line on an area image map of the complete pattern repeat, means for relatively moving the operation effector and material in the direction of pattern repeat, the machine vision system being operable to scan the material during the relative movement, comparison means comparing the scanning image with the map to determine the relative positions of the material and the operation effector, and guidance means for the operation effector to effect the operation at a position on the material corresponding to the path define on the map.